Instructions are providing for filling out the JWST APT observing template for the NIRCam WFSS Deep Galaxy Observations example science program, consisting of NIRCam WFSS observations. The steps below roughly follow those given in NIRCam Wide Field Slitless Spectroscopy APT Template.

Dated material

This example program was constructed pre-launch, and details may be out of date with actual observatory performance. However, it still provides a useful example for training purposes.

Please refer to JWST Example Science Programs for more information.

On this page

APT file

A filled out APT file can be accessed via the APT menu options File → JWST Example Science Proposals → NIRCam → 37 NIRCam WFSS Deep Galaxy Observations. The APT file was created with version 27.3. There may be inconsistencies or additional warnings or errors with other versions of APT.

Fill out Proposal Information

Words in bold are GUI menus/
panels or data software packages;
bold italics are buttons in GUI
tools or package parameters.

After opening APT, select New JWST Proposal under the New Document pull-down menu. On the Proposal Information page, enter Title, Abstract, and Category of proposal and kept Cycle number at its default value.

Enter proposed target

See also: APT Targets

This program is targeting SDSS J0100+2802, a z > 6 quasar at RA = 01 00 13.02, Dec = 28 02 25. In Targets, create a new Fixed Target with those coordinates and provide a name J0100+2802 (abbreviated as spaces are not allowed in APT target names).

Observations

See also: APT Observations

In Observations, create a new Observation Folder. Observation 1 will be created automatically. Select NIRCam Wide Field Slitless Spectroscopy as the Template and select the Target defined above.

Instrument: NIRCAM
Template: NIRCam Wide Field Slitless Spectroscopy
Target: J0100+2802

Complete APT observation template for NIRCam WFSS observations

Proceed to the NIRCam Wide Field Slitless Spectroscopy tab (leftmost tab on the lower half of the APT screen). Since a wide observing area is desired (saturation is not a concern for these faint targets), choose Module = ALL and Subarray = FULL to cover a larger field of view. For the Grism (long wavelength), select GRISMR as discussed in the introduction.

Module: ALL
Subarray: FULL
Grism (Long Wavelength): GRISMR

Dither patterns

As discussed in the intro article, this program uses 3 INTRAMODULEX primary dithers and 4 standard subpixel dithers, for a total of 12 dithered exposures.

Dither Parameters:

Primary Dither Type: INTRAMODULEX
Primary Dithers: 3
Subpixel Positions: 4-Point

Science (grism) exposures

Enter the WFSS exposure parameters determined in our ETC Calculations (Calculation #1). Again note the full WFSS F356W exposure time is divided in 2: the first half with simultaneous F115W imaging and the second with F200W imaging.

Direct Image	Long Filter	Short Filter	Readout Pattern	Groups	Integrations	ETC Wkbk.Calc ID
	F356W	F115W	SHALLOW4	6	1	26201.1
✓	F356W	F200W	SHALLOW4	6	1	26201.1

The first column indicates that a single direct image will be obtained after the final WFSS exposure, as required. This program forgoes the option of obtaining an additional direct image after the first set of exposures (F356W GRISMR and F115W imaging).

Direct image exposures

Next, enter the direct image exposure parameters determined in our ETC Calculation #2.

Long Filter	Short Filter	Readout Pattern	Groups	Integrations	ETC Wkbk.Calc ID
F356W	F200W	SHALLOW4	10	1	26201.2

Exposure sequence display

Given the inputs above, the display below will automatically populate showing the sequence of exposures. Note that after the direct image, 2 out-of-field images are obtained with the same exposure specifications.

Sequence	Exposure Type	Long Wavelength	Short Wavelength	Readout Pattern	Groups	Dithers	Total Exposure Time
1	Grism & Imaging	GRISMR + F356W	F115W imaging	SHALLOW4	6	12	3736 s
2	Grism & Imaging	GRISMR + F356W	F200W imaging	SHALLOW4	6	12	3736 s
2	Direct Image	F356W imaging	F200W imaging	SHALLOW4	10	1	526 s
2	Out of Field	F356W imaging	F200W imaging	SHALLOW4	10	2	1052 s

Define mosaic strategy

The above observation sequence will be repeated 4 times in a 2 × 2 mosaic, as described in the introduction. The mosaic tiles will be spread to cover more area and capture more high redshift galaxies surrounding the primary target quasar. But the mosaic tiles will also overlap such that every observation will include the quasar. The desired mosaic coverage is implemented as follows in APT and shown below in Figure 1.

Under the Mosaic Properties tab:

Rows: 2
Columns: 2
Row Overlap %: 45
Column Overlap %: 72
Row shift: 0
Column shift: -1.2° (rotation)

The overlap and shift values can be determined by trial and error after inspecting the results in APT Aladin. The final entry (column shift) makes the final mosaic a bit more symmetric (rectangular) as there are slight asymmetries in the NIRCam Field of View.

APT screenshot of the final 2 × 2 mosaic, with each tile consisting of 12 dither positions, 1 direct image, and 2 out-of-field images. Darker regions correspond to greater exposure time in the long wavelength channel. The short wavelength observations are not shown, for clarity.

Define special requirements

To recenter the target within the mosaicked observations, a small offset of (4", -3.5") in (X, Y) is added via the Special Requirements tab (again determined by trial and error inspecting the output in APT Aladin).

Finally, the Aperture PA Range was restricted to include other targets of interest. Two options are provided: 60–65 degrees and 230–240 degrees.

Run Visit Planner

See also: APT Visit Planner

To determine the visibility window of the proposed observation and ensure that guide stars can be found, run the Visit Planner Tool by clicking the Visit Planner icon in the top toolbar, selecting the observation, and clicking Update Display. The Visit Planner confirms observable windows totaling over 2 months per year.

Note after updating the display, there is no need to run Smart Accounting (the option is grayed out).

View Observations in Aladin

See also: APT Aladin Viewer

In the top toolbar, click View in Aladin to see the observations oriented on the sky in a new window. Then in that window, click DSS in the top toolbar to see the observations overlaid on images from the Digital Sky Survey.

Note the orientation (rotation) is 62.5 degrees, the middle of the first range of position angles input as an option.

Notable updates
Originally published	10 Feb 2018

JWST User Documentation

Step-by-Step APT Guide for NIRCam WFSS Deep Galaxy Observations